U.S. Pat. Nos. 4,187,167 and particularly 4,280,892 to J. J. Havlik, describe apparatus and methods for the separation of crude petroleum from tar sands and the like. The present invention, by the same inventor, provides an improvement in these apparatus and methods. Both these prior patents provide mechanical devices for the heat treatment of tar sands. After experimentation, it has been found that the devices each suffer a number of disadvantages in transporting the tar and materials through heated zones. These disadvantages include preventing jamming of the apparatus with the tar sands, providing for controlled feeding and withdrawl of the tar sands through the apparatus, maintaining desired heating of the tar sands, and providing an apparatus which can readily be expanded to meet increased flow rates.